Mechanism of rate cording and recruitment in motor units of lower extremity muscle during walking in human

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The purpose of this study was to clarify the control over recruitment and firing rate of motor units of lower extremity (LE) muscles during free or different walking speeds in young adult and elderly. The frequency obtained surface electromyography (EMG) was calculated by MemCalc which was nonlinear system software. The results were as followed.EMG activities of LE muscles during early stance phase were greater than those during swing phase in walking cycle.It was considered that the greater EMG activities of TA for early stance phase was controlled in the same rates of recruitment between the larger motor units in fast-twitch muscle fibers and smalier motor units in slow-twitch muscle fibers during free walking. The greater EMG activity of VL in early stance phase was significantly controlled to recruit the larger motor units in fast-twitch muscle fibers, inhibiting recruitment of the smaller motor units in slow-twitch muscle fibers selectively. On the other hand, the greater EMG acti … More vity of MH in early stance phase was significantly controlled to recruit the smaller motor units in slow-twitch muscle fibers, inhibiting recruitment of the larger motor units in fast-twitch muscle fibers selectively.The MG was constantly activated during stance phase, the activity in mid stance phase was greatest it was considered that the greater EMG activity of MG for early stance phase was controlled to recruit the larger motor units in fast-twitch muscle fibers, and this greater activity was important to transfer to push-off during stance phase.The characteristics of each muscle EMG activity tended to be similar in different walking speeds.The EMG activities in the elderly (over 65 years) were greater than those in young adult The controls were different in each muscle. It was suggested that the TA in the elderly was controlled in the same rates of recruitment between the fast-twitch muscle fibers and the slow-twitch muscle fibers during free walking.On the other hand, it was suggested that the MG and MH in the elderly were controlled to recruit the larger motor units in fast-twitch muscle fibers and the VL in the elderly was selectively controlled to recruit the smaller motor units in slow-twitch muscle fibers during free walking. Less